JP4826507B2 - Focus detection apparatus and imaging apparatus - Google Patents

Description

  The present invention relates to a focus detection element, a focus detection device, and an imaging device.

  A focus detection element is known in which a plurality of focus detection pixels that receive light from an imaging optical system are two-dimensionally arranged in a dense square lattice (see, for example, Patent Document 1). In this focus detection element, two pairs of photoelectric conversion units are arranged in one focus detection pixel, thereby enabling focus detection with the same detection pitch in two directions on the screen by the imaging optical system.

Prior art documents related to the invention of this application include the following.
JP 58-024105 A

However, in the conventional focus detection element described above, since two pairs of photoelectric conversion units are arranged in one focus detection pixel, focus detection is performed by reducing the focus detection pixel in order to increase focus detection accuracy. There is a limit to reducing the pitch.
Assuming that the focus detection pixels arranged in a two-dimensional manner have a pair of photoelectric conversion units and perform focus detection in two vertical and horizontal directions on the screen using different focus detection pixels. When the focus detection pixels are set to be continuous pixels along the arrangement direction of the focus detection pixels so that the pitch is as small as possible, and the vertical and horizontal focus detection pixel arrays are set to intersect, Since the pixel located at the intersection is a pixel in any direction, the detection pitch cannot be made the same depending on the arrangement direction of the focus detection pixels.

The invention according to claim 1 is based on a focus detection element in which a plurality of focus detection pixels that receive light from the imaging optical system are densely arranged in a square lattice, and an output signal from the focus detection element, And a plurality of focus detection pixels arranged in a first direction that forms an angle of 45 degrees with one dense direction of the square lattice. A first focus detection pixel and a plurality of second focus detection pixels arranged in a second direction orthogonal to the first direction, and the first focus detection pixel is the square lattice. Are arranged every other pixel in two dense directions orthogonal to each other, and the second focus detection pixels are arranged in the two dense directions perpendicular to the square lattice at positions where the first focus detection pixels are not arranged. The first focus is arranged every other pixel. The output pixel has a pair of photoelectric conversion units divided in a direction perpendicular to the first direction, and the second focus detection pixel is a pair of pixels divided in a direction perpendicular to the second direction. A photoelectric conversion unit, and the focus detection unit performs focus detection based on output signals of the pair of photoelectric conversion units of the first focus detection pixel and the pair of photoelectric conversions of the second focus detection pixel. The focus detection is performed based on the output signal of the unit.
The invention of claim 3 is based on a focus detection element in which a plurality of focus detection pixels that receive light from the imaging optical system are densely arranged in a square lattice, and an output signal from the focus detection element, And a plurality of focus detection pixels arranged in a first direction that forms an angle of 45 degrees with one dense direction of the square lattice. A first focus detection pixel and a plurality of second focus detection pixels arranged in a second direction orthogonal to the first direction, and the first focus detection pixel is the square lattice. Are arranged every other pixel in two dense directions orthogonal to each other, and the second focus detection pixels are arranged in the two dense directions perpendicular to the square lattice at positions where the first focus detection pixels are not arranged. The first focus is arranged every other pixel. When the pixel area is divided in a direction perpendicular to the first direction, the output pixel has a first pixel having a photoelectric conversion unit in one region and a photoelectric conversion unit in a region on the other side. And the first and second pixels are alternately arranged, and the second focus detection pixel is arranged on one side when the pixel region is divided in a direction perpendicular to the second direction. A first pixel having a photoelectric conversion unit in the region and a second pixel having a photoelectric conversion unit in the other side region, the first and second pixels being alternately arranged, and the focus detection means The focus detection is performed based on the output signals of the photoelectric conversion units of the first and second pixels of the first focus detection pixel, and the photoelectric conversion units of the first and second pixels of the second focus detection pixel are detected. Focus detection is performed based on the output signal.
  The invention according to claim 5 is based on a focus detection element in which a plurality of focus detection pixels that receive light from the imaging optical system are densely arranged in a grid of a dense hexagonal lattice, and an output signal from the focus detection element. And a focus detection means for performing focus detection of the imaging optical system, wherein the plurality of focus detection pixels are arranged in a first direction that forms an angle of 30 degrees with one dense direction of the dense hexagonal lattice. A plurality of first focus detection pixels, a plurality of second focus detection pixels arranged in a second direction that forms an angle of 60 degrees with the first direction, and the first direction and the second direction. And a plurality of third focus detection pixels arranged in a third direction having an angle of 60 degrees, and the first focus detection pixels are arranged every two pixels in the three dense directions of the dense hexagonal lattice. And the second focus detection pixel is used for the first focus detection. The third focus detection pixels are arranged at intervals of two pixels in the three dense directions of the dense hexagonal lattice at positions where no element is arranged, and the third focus detection pixels are the first focus detection pixels and the second focus detection pixels. The first focus detection pixels are arranged at intervals of two pixels in three dense directions of the dense hexagonal lattice at positions where they are not arranged, and the first focus detection pixels have a pair of photoelectric conversion units divided in a direction perpendicular to the first direction. The second focus detection pixel includes a pair of photoelectric conversion units divided in a direction perpendicular to the second direction, and the third focus detection pixel is perpendicular to the third direction. A pair of photoelectric conversion units divided in a direction, wherein the focus detection unit performs focus detection based on an output signal of the pair of photoelectric conversion units of the first focus detection pixel, and the second focus detection pixel; Output signals of the pair of photoelectric conversion units Based detected focus, characterized by focus detection based on the pair of output signals of the photoelectric conversion portion of the third focus detection pixels.
The invention according to claim 7 is based on a focus detection element in which a plurality of focus detection pixels that receive light from the imaging optical system are densely arranged in a grid of a dense hexagonal lattice, and an output signal from the focus detection element And a focus detection means for performing focus detection of the imaging optical system, wherein the plurality of focus detection pixels are arranged in a first direction that forms an angle of 30 degrees with one dense direction of the dense hexagonal lattice. A plurality of first focus detection pixels, a plurality of second focus detection pixels arranged in a second direction that forms an angle of 60 degrees with the first direction, and the first direction and the second direction. And a plurality of third focus detection pixels arranged in a third direction having an angle of 60 degrees, and the first focus detection pixels are arranged every two pixels in the three dense directions of the dense hexagonal lattice. And the second focus detection pixel is used for the first focus detection. The third focus detection pixels are arranged at intervals of two pixels in the three dense directions of the dense hexagonal lattice at positions where no element is arranged, and the third focus detection pixels are the first focus detection pixels and the second focus detection pixels. When the pixel region is divided in the direction perpendicular to the first direction, the first focus detection pixels are arranged at intervals of two pixels in the three dense directions of the dense hexagonal lattice at positions where they are not arranged. A first pixel having a photoelectric conversion unit in a region on the side and a second pixel having a photoelectric conversion unit in a region on the other side, wherein the first and second pixels are alternately arranged, When the pixel area is divided in a direction perpendicular to the second direction, the focus detection pixel has a first pixel having a photoelectric conversion unit in one area and a photoelectric conversion section in the other area. A second pixel, the first and Two pixels are alternately arranged, and the third focus detection pixel includes a first pixel having a photoelectric conversion unit in one region when the pixel region is divided in a direction perpendicular to the third direction. A second pixel having a photoelectric conversion unit in the other side region, the first and second pixels are alternately arranged, and the focus detection unit is configured to detect the first focus detection pixel. And focus detection based on the output signal of the photoelectric conversion unit of the second pixel, focus detection based on the output signal of the photoelectric conversion unit of the first and second pixels of the second focus detection pixel, and the third focus The focus detection is performed based on the output signals of the photoelectric conversion units of the first and second pixels of the detection pixel.

  According to the present invention, it is possible to realize focus detection with high accuracy in a plurality of directions on the screen.

  As an imaging apparatus including the focus detection element and the focus detection apparatus according to one embodiment, a lens interchangeable digital still camera will be described as an example. The present invention is not limited to the interchangeable lens camera, but can be applied to a fixed lens camera. FIG. 1 is a cross-sectional view showing a configuration of a camera according to an embodiment. A digital still camera 201 according to an embodiment includes an interchangeable lens 202 and a camera body 203, and the interchangeable lens 202 is attached to the camera body 203 via a mount unit 204.

  The interchangeable lens 202 includes a lens 209, a zooming lens 208, a focusing lens 210, an aperture 211, a lens drive control device 206, and the like. The lens drive control device 206 includes a microcomputer (not shown), a memory, a drive control circuit, and the like. The lens drive control device 206 controls the driving of the focusing lens 210 and the aperture 211, detects the state of the zooming lens 208, the focusing lens 210, and the aperture 211, and the like. In addition, the lens information is transmitted and the camera information is received by communication with a body drive control device 214 described later.

  The camera body 203 includes a body drive control device 214, a liquid crystal display element drive circuit 215, a liquid crystal display element 216, an eyepiece lens 217, a memory card 219, an image sensor 220, a focus detection element 221, a light splitting prism 223, and the like.

  The light splitting prism 223 includes a half mirror surface 222 that splits the light beam coming from the interchangeable lens 202 into a reflected light beam and a transmitted light beam in a ratio of 1: 1. The imaging element (solid-state imaging element) 220 has imaging pixels arranged in a two-dimensional manner (details will be described later), and is disposed on a planned imaging plane (imaging plane) of a light beam that has passed through the light splitting prism 223. On the other hand, the focus detection element 223 has focus detection pixels arrayed two-dimensionally (details will be described later), and is disposed on the planned imaging plane of the light beam reflected by the light splitting prism 223.

  The body drive control device 214 includes a microcomputer, a memory, a drive control circuit, and the like. The drive control of the image sensor 220 and the focus detection element 221, readout of the image signal and focus detection signal, processing and recording of the image signal, focus detection signal. Based on the focus detection calculation, the focus adjustment of the interchangeable lens 202, and the camera operation control. The body drive control device 214 communicates with the lens drive control device 206 via the electrical contact 213 to receive lens information and send camera information (defocus amount, aperture value, etc.).

  The liquid crystal display element 216 functions as a liquid crystal viewfinder (EVF: electrical viewfinder). The liquid crystal display element driving circuit 215 displays the through image by the image sensor 220 on the liquid crystal display element 216, and the photographer can observe the through image through the eyepiece lens 217. The memory card 219 is an image storage that stores an image captured by the image sensor 220.

  A subject image is formed on the light receiving surfaces of the imaging element 220 and the focus detection element 221 by the light beam that has passed through the interchangeable lens 202 and is split by the light splitting prism 223. The subject image is photoelectrically converted by the image sensor 220 and the focus detection element 221, and the image signal and the focus detection signal are sent to the body drive control device 214.

  The body drive control device 214 calculates the defocus amount based on the focus detection signal from the focus detection element 220 and sends this defocus amount to the lens drive control device 206. In addition, the body drive control device 214 processes the image signal from the image sensor 220 and stores it in the memory card 219, and sends the through image signal from the image sensor 220 to the liquid crystal display element drive circuit 215, so that the through image is liquid crystal. The image is displayed on the display element 216. Further, the body drive control device 214 sends aperture control information to the lens drive control device 206 to control the aperture of the aperture 211.

  The lens drive control device 206 changes the lens information according to the focusing state, zooming state, aperture setting state, aperture open F value, and the like. Specifically, the positions of the zooming lens 208 and the focusing lens 210 and the aperture value of the aperture 211 are detected, and lens information is calculated according to these lens positions and aperture values, or a lookup prepared in advance. Lens information corresponding to the lens position and aperture value is selected from the table.

  The lens drive control device 206 calculates a lens drive amount based on the received defocus amount, and drives the focusing lens 210 to a focal point according to the lens drive amount. Further, the lens drive control device 206 drives the diaphragm 211 in accordance with the received diaphragm value.

  FIG. 2 shows an arrangement range of imaging pixels and focus detection pixels on the imaging screen of the interchangeable lens 201. On the imaging screen of the interchangeable lens 201, the imaging pixels of the imaging element 220 are arranged in the range 220a, and the focus detection pixels of the focus detection element 221 are arranged in the range 221a. The focus detection pixel array range 221a is narrower than the imaging pixel array range 220a. Since focus detection is rarely performed at the edge of the photographing screen, the focus detection element 221 is downsized by narrowing the focus detection pixel array range 221a.

  In FIG. 2, the point 100 is the center of the photographing screen, that is, the intersection of the optical axis of the interchangeable lens 202 and the image sensor 220, the straight line 101 is a horizontal (row direction) straight line passing through the point 100, and the straight line 102 is a point. 100 is a straight line passing through 100 in the vertical direction (column direction). The upward direction of the straight line 102 is the “A” direction shown in FIG. 1, and the downward direction is the “B” direction shown in FIG.

  FIG. 3 is a partially enlarged view of the image sensor 220. The image sensor 220 includes imaging pixels arranged in a two-dimensional shape in a row direction and a column direction perpendicular to the row direction in a dense square lattice pattern. In FIG. 3, the imaging pixels are densely arranged in the row direction and the column direction, and the dense arrangement directions of the imaging pixels are the row direction and the column direction.

  FIG. 8 is an enlarged view of a unit array portion in the image pickup pixel array of the image sensor 220. As shown in FIG. 8, the image sensor 220 is configured in a Bayer array in which three types of four pixels for imaging, which are green pixels 310 and 313, a red pixel 311, and a blue pixel 312, are used as a unit array. Each imaging pixel includes a microlens 10, a photoelectric conversion unit 11, and a color filter (not shown). There are three types of color filters, red (R), green (G), and blue (B), and the respective spectral sensitivities have the characteristics shown in FIG.

  FIG. 4 is an enlarged view of a part of the focus detection element 221 (region C shown in FIG. 2). In the focus detection element 221, two types of focus detection pixels 320 and 330 are arranged in a two-dimensional shape in the row direction and in the column direction perpendicular to the row direction in a dense square lattice pattern. The array of focus detection pixels of the focus detection element 221 includes a partial array 221a composed of focus detection pixels 320 shown in FIG. 5 and a partial array 221b composed of focus detection pixels 330 shown in FIG.

  In FIG. 5, the focus detection pixel 320 constituting one partial array 221a rotates the focus detection pixel including the microlens 10 and the pair of photoelectric conversion units 12 and 13 shown in FIG. 9 by 45 degrees in the clockwise direction. It has been made. In FIG. 6, the focus detection pixels 330 constituting the other partial array 221 b are arranged so that the focus detection pixels including the microlens 10 and the pair of photoelectric conversion units 12 and 13 illustrated in FIG. 9 are counterclockwise. It is rotated 45 degrees.

  The focus detection pixels 320 and 330 are not provided with a color filter in order to increase the amount of light, and the spectral characteristics thereof are the spectral sensitivity characteristics of a photodiode that performs photoelectric conversion, and the spectral characteristics of an infrared cut filter (not shown). The spectral characteristics shown in FIG. The spectral characteristics of the focus detection pixels 320 and 330 are spectral characteristics obtained by adding the spectral characteristics of the green pixel G, the red pixel R, and the blue pixel B shown in FIG. 10, and the light wavelength region of the sensitivity is the green pixel G. The optical wavelength region of the sensitivity of the red pixel R and the blue pixel B is included.

  In the partial array 221a shown in FIG. 5, as shown in FIG. 7, the inter-pixel distance between the focus detection pixels 320 is S2. In FIG. 7, when the shortest inter-pixel distance in the dense square lattice arrangement is S1, the inter-pixel distance S2 is the shortest inter-pixel distance after the inter-pixel distance S1. In the dense square lattice arrangement, for example, when P is the shortest inter-pixel distance S1, the second shortest inter-pixel distance S2 is √ (2) · P. In the partial array 221a, a column of focus detection pixels 320 arranged on a straight line in the direction D1 (a direction rotated 45 degrees counterclockwise from the vertical direction) forms one focus detection pixel column, and a pupil to be described later The image shift amount in the direction D1 of the pair of images on the shooting screen is detected by the division method.

  In the partial array 221b shown in FIG. 6, the inter-pixel distance between the focus detection pixels 330 is S2, as shown in FIG. The inter-pixel distance S2 is the shortest inter-pixel distance next to the inter-pixel distance S1, where S1 is the shortest inter-pixel distance in the dense square lattice array as described above. In the partial array 221b, a column of focus detection pixels 330 arranged on a straight line in the direction D2 (a direction rotated 45 degrees clockwise from the vertical direction, a direction orthogonal to the direction D1) is one focus detection pixel column. The image shift amount in the direction D2 of the pair of images on the photographing screen is detected by a pupil division method described later.

  When the partial array 221a shown in FIG. 5 and the partial array 221b shown in FIG. 6 are combined, the focus detection elements 221 in which the focus detection pixels 320 and 330 shown in FIG. 4 are arranged in a dense square lattice are formed. The focus detection element 221 having the pixel arrangement shown in FIG. 4 can detect image misalignment in the D1 direction and the D2 direction at an arbitrary position on the shooting screen.

  The imaging pixels 310, 311, 312, and 313 shown in FIG. 8 and the focus detection pixels 320 and 330 shown in FIG. 9 are shown in the same scale, and the area of the light receiving surface of the focus detection pixels 320 and 330 is the imaging. It is wider than the area of the light receiving surface of the pixels 310, 311, 312, 313. For example, when the diameter of the light receiving surface of the imaging pixels 310, 311, 312, and 313 is 3 microns, the diameter of the light receiving surface of the focus detection pixels 320 and 330 is 6 microns.

  The photoelectric conversion units 11 of the imaging pixels 310, 311, 312, and 313 are designed to have a shape that receives all the light flux having a predetermined aperture diameter (for example, F1.0) by the microlens 10. On the other hand, the pair of photoelectric conversion units 12 and 13 of the focus detection pixels 320 and 330 are designed to receive all light beams having a predetermined aperture diameter (for example, F2.8) by the microlens 10. When the size of the focus detection pixels 320 and 330 is reduced (for example, when it becomes several microns or less), a pupil division function, which will be described later, deteriorates due to the influence of diffraction, and the focus detection accuracy deteriorates. Since the output level of 330 decreases and the focus detection capability at low luminance deteriorates, focus detection is performed more than the light receiving surface size of the imaging pixels 310, 311, 312, and 313 reduced for improving the resolution performance. The size of the light receiving surface of the pixel is increased to achieve both image performance and focus detection performance.

  FIG. 12 is a cross-sectional view of the imaging pixels 310, 311, 312, and 313. In the imaging pixels 310, 311, 312, and 313, the microlens 10 is disposed in front of the imaging photoelectric conversion unit 11, and the photoelectric conversion unit 11 is projected forward by the microlens 10. The photoelectric conversion unit 11 is formed on the semiconductor circuit substrate 29. A color filter (not shown) is disposed at an intermediate position between the microlens 10 and the photoelectric conversion unit 11.

  FIG. 13 is a cross-sectional view of the focus detection pixels 320 and 330. In the focus detection pixels 320 and 330, the microlens 10 is disposed in front of the focus detection photoelectric conversion units 12 and 13, and the photoelectric conversion units 12 and 13 are projected forward by the microlens 10. The photoelectric conversion units 12 and 13 are formed on the semiconductor circuit substrate 29.

  Next, a focus detection method by a pupil division method using a microlens will be described with reference to FIG. In FIG. 14, the optical-axis microlens 50 of the interchangeable lens 202 (see FIG. 1), the microlens 60 adjacent thereto, and the corresponding photoelectric conversion units (52, 53), (62,63). This will be described as a representative. The exit pupil 90 is set to a distance d0 in front of the microlenses 50 and 60 arranged on the planned imaging plane of the interchangeable lens 202 shown in FIG. This distance d0 is a distance determined according to the curvature and refractive index of the microlenses 50 and 60, the distance between the microlens and the photoelectric conversion unit, and is referred to as a distance measuring pupil distance in this specification.

  The microlenses 50 and 60 are disposed in the vicinity of the planned imaging plane of the interchangeable lens 202 (imaging optical system) shown in FIG. The shape of the pair of photoelectric conversion units 52 and 53 disposed behind the microlens 50 is projected onto the exit pupil 90 separated from the microlens 50 by the projection distance d0 by the microlens 50, and the projected shape is a pair. (Referred to as distance measuring pupil in this specification) 92, 93. Similarly, the shape of the pair of photoelectric conversion units 62 and 63 disposed behind the microlens 60 is projected onto the exit pupil 90 separated from the microlens 60 by the projection distance d0 by the microlens 60, and the projected shape thereof. Forms distance measuring pupils 92 and 93.

  In FIG. 14, for the sake of convenience, a focus detection pixel (consisting of a microlens 50 and a pair of photoelectric conversion units 52 and 53) on the optical axis is adjacent to a focus detection pixel (a microlens 60 and a pair of photoelectric conversion units 62). 63). However, even when the focus detection pixel is at a position away from the optical axis at the periphery of the screen, each pair of photoelectric conversion units is separated from each pair of distance measurement pupils. A light beam arriving at each microlens is received.

  Here, the arrangement direction of the focus detection pixels is made to coincide with the arrangement direction of the pair of distance measuring pupils, that is, the arrangement direction of the pair of photoelectric conversion units.

  The projection direction of each pixel is determined so that the projection shapes (ranging pupils 92 and 93) of the photoelectric conversion units of the focus detection pixels coincide on the exit pupil 90 at the projection distance d0. That is, the pair of distance measuring pupils 92 and 93, the pair of photoelectric conversion units (52 and 53), and the pair of photoelectric conversion units (62 and 63) have a conjugate relationship via the microlenses 50 and 60. ing.

  The photoelectric conversion unit 52 outputs a signal corresponding to the intensity of an image formed on the microlens 50 by the focus detection light beam 72 passing through the distance measuring pupil 92 and directed to the microlens 50. Similarly, the photoelectric conversion unit 53 outputs a signal corresponding to the intensity of the image formed on the microlens 50 by the focus detection light beam 73 passing through the distance measuring pupil 93 and directed to the microlens 50. In addition, the photoelectric conversion unit 62 outputs a signal corresponding to the intensity of the image formed on the microlens 60 by the focus detection light beam 82 that passes through the distance measuring pupil 92 and faces the microlens 60. Similarly, the photoelectric conversion unit 63 outputs a signal corresponding to the intensity of the image formed on the microlens 60 by the focus detection light beam 83 passing through the distance measuring pupil 93 and directed toward the microlens 60.

  A plurality of focus detection pixels are arranged in a straight line, and the output of a pair of photoelectric conversion units of each pixel is collected into an output group corresponding to the distance measurement pupil 92 and the distance measurement pupil 93, thereby providing a distance measurement pupil. Information about the intensity distribution of a pair of images formed on the focus detection pixel array by the focus detection light fluxes that respectively pass through 92 and the distance measuring pupil 93 is obtained. By applying an image shift detection calculation process (correlation calculation process, phase difference detection process), which will be described later, to this information, the image shift amount of a pair of images is detected by a so-called pupil division type phase difference detection method.

  Further, by performing a conversion operation according to the center of gravity distance of the pair of distance measuring pupils to the image shift amount, the current image plane relative to the planned image plane (corresponding to the position of the microlens array on the planned image plane) The deviation (defocus amount) of the imaging plane at the focus detection position is calculated.

  In the above description, the range-finding pupil is not limited by the aperture limiting element (aperture aperture, lens outline, hood, etc.) of the interchangeable lens, but is measured by the aperture limiting element of the interchangeable lens. When the distance pupil is restricted, the photoelectric conversion unit of the focus detection pixel receives the light beam passing through the restricted distance measurement pupil as the focus detection light beam.

  When the size of the focus detection pixel is reduced (several microns or less), the aperture diameter of the microlens decreases proportionally, and distance measurement is performed when a pair of photoelectric conversion units are projected onto the exit pupil by the microlens. Since the shapes of the pupils 92 and 93 are greatly blurred due to diffraction, separation of the distance measuring pupils 92 and 93 becomes increasingly difficult, and as a result, focus detection accuracy is lowered.

  Next, the relationship between the imaging pixels and the exit pupil will be described with reference to FIG. In FIG. 15, the same elements as those shown in FIG. 14 are denoted by the same reference numerals, and different points will be mainly described. 15 schematically illustrates an imaging pixel (comprising a microlens 70 and a photoelectric conversion unit 71) on the optical axis of the interchangeable lens 202 illustrated in FIG. 1, but photoelectric imaging is also performed in other imaging pixels. Each of the converters receives a light beam coming from each region 94 to each microlens.

  The microlens 70 is disposed in the vicinity of the planned imaging plane of the interchangeable lens 202 (imaging optical system) shown in FIG. The shape of the photoelectric conversion unit 71 disposed behind the microlens 70 is projected onto the exit pupil 90 separated from the microlens 70 by the projection distance d0 by the microlens 70, and the projection shape forms a region 94. The photoelectric conversion unit 71 outputs a signal corresponding to the intensity of the image formed on the microlens 70 by the focus detection light beam 81 that passes through the region 94 of the exit pupil 90 and faces the microlens 70. By arranging a large number of such imaging pixels two-dimensionally, image information can be obtained based on the photoelectric conversion unit of each pixel.

  FIG. 16 is a front view of the distance measuring pupil on the exit pupil plane. In FIG. 16, the circumscribed circle of the distance measuring pupils 922 and 933 obtained by projecting a pair of photoelectric conversion units from the focus detection pixels onto the exit pupil plane 90 by the microlens is a predetermined aperture F value when viewed from the imaging plane. (In this specification, it is called a distance-measuring pupil F value. Here, it is F2.8). A region 901 indicated by a broken line in the drawing indicates a region corresponding to an aperture value (for example, F2) having an aperture diameter larger than the aperture value F2.8, and includes distance measuring pupils 922 and 933 therein. The distance between the centers of gravity 952 and 953 of the light beams (focus detection light beams) passing through the distance measurement pupils 922 and 933 in the direction in which the distance measurement pupils 922 and 933 are aligned (horizontal direction in the figure) is G.

  FIG. 17 is a flowchart showing the operation of the camera (imaging device) shown in FIG. The body drive control device 214 starts this operation when a power switch (not shown) of the camera is turned on in step 100. In step 110, subject brightness is detected based on the output signal level of the image sensor 220, and image data is read by controlling the image sensor 220 in accordance with the subject brightness. In the next step 120, the image pickup pixel data of the image sensor 220 is displayed on the electronic viewfinder. In step 130, the focus detection element 221 is controlled in accordance with the subject brightness to read out focus detection image data.

  In step 140, a pair of image data corresponding to the array of focus detection pixels 320 in the direction D1 in a region near an arbitrarily designated position (determined manually or automatically) on the photographing screen, and the direction D2 Based on a pair of image data corresponding to the arrangement of the focus detection pixels 330, an image shift detection calculation process (correlation calculation process) described later is performed, and the defocus amount in the direction D1 and the defocusing direction in the direction D2 at the designated position. Calculate the focus amount. Furthermore, one defocus amount is finally obtained based on the two defocus amounts. For example, an average value of two defocus amounts, a defocus amount indicating a closer object, or a more reliable defocus amount is set as a final defocus amount.

  In step 150, it is determined whether or not the focus is close, that is, whether or not the absolute value of the defocus amount is within a predetermined value. If it is determined that the lens is not in focus, the process proceeds to step 160 where the defocus amount is transmitted to the lens drive controller 206 (see FIG. 1), and the focusing lens 210 of the interchangeable lens 202 is driven to the focus position. Then, it returns to step 110 and repeats the operation | movement mentioned above. Even when focus detection is impossible, the process branches to this step, a scan drive command is transmitted to the lens drive control device 206, and the focusing lens 210 of the interchangeable lens 202 is scan-driven between infinity and close. Then, it returns to step 110 and repeats the operation | movement mentioned above.

  On the other hand, if it is determined that it is close to the in-focus state, the process proceeds to step 170, and it is determined whether or not a shutter release has been performed by operating a shutter button (not shown). If it is determined that the release operation has not been performed, the process returns to step 110 to repeat the above-described operation. If it is determined that the release operation has been performed, the process proceeds to step 180, the shooting parameters are determined according to the subject brightness, the aperture control information is transmitted to the lens drive control device 206, and the aperture value of the interchangeable lens 202 is set to the shooting aperture value. To do. When the aperture control is completed, the image sensor is exposed according to the determined charge accumulation time. In step 190, data of the image pickup pixel is read from the image pickup element 220, and in step 200, the image data is stored in the memory card 219. Then, it returns to step 110 and repeats the operation | movement mentioned above.

The details of the image shift detection calculation process (correlation calculation process) executed in step 140 of FIG. 17 will be described with reference to FIG. A pair of data strings (α1 to αM, β1 to βM, where M is the number of data) output from the focus detection pixel column is subjected to a high frequency cut filter process as shown in Equation (1), and the first data string A1 to AN and second data strings B1 to BN are generated.
An = αn + 2 × αn + 1 + αn + 2,
Bn = βn + 2 × βn + 1 + βn + 2 (1)
In the formula (1), n = 1 to N. As a result, noise components and high-frequency components that adversely affect the correlation processing can be removed from the data string.

  Here, α1 to αM correspond to image data of an image formed by the focus detection light beam passing through the distance measuring pupil 92 shown in FIG. 14, and β1 to βM are determined by the focus detection light beam passing through the distance measurement pupil 93. This corresponds to the image data of the formed image. Note that this processing can be omitted when the calculation time is to be shortened or when it is already known that there is little high-frequency component since the focus is greatly defocused.

The correlation calculation shown in the equation (2) is performed on the data strings An and Bn, and the correlation amount C (k) is calculated.
C (k) = Σ | An−Bn + k | (2)
In equation (2), Σ operations are accumulated for n. The range of n is limited to the range in which data of An and Bn + k exist according to the shift amount k. The shift amount k is an integer and is a relative shift amount with the data interval (pixel pitch) of the data string as a unit. As shown in FIG. 18A, the calculation result of the expression (2) indicates that the correlation amount C (k) is the shift amount (k = kj = 2 in FIG. Minimal (the smaller the value, the higher the degree of correlation).

Next, the shift amount x that gives the minimum value C (x) with respect to the continuous correlation amount is obtained by using the three-point interpolation method according to the equations (3) to (6).
x = kj + D / SLOP (3),
C (x) = C (kj) − | D | (4),
D = {C (kj-1) -C (kj-1)} / 2 (5),
SLOP = MAX {C (kj + 1) -C (kj), C (kj-1) -C (kj)} (6)

  Whether or not the shift amount x calculated by the equation (3) is reliable is determined as follows. As shown in FIG. 18B, when the degree of correlation between a pair of data is low, the value of the minimal value C (x) of the interpolated correlation amount increases. Therefore, when C (x) is equal to or greater than a predetermined threshold value, it is determined that the calculated shift amount has low reliability, and the calculated shift amount x is canceled. Alternatively, in order to normalize C (x) with the contrast of data, when the value obtained by dividing C (x) by SLOP that is proportional to the contrast is equal to or greater than a predetermined value, the reliability of the calculated shift amount Is determined to be low, and the calculated shift amount x is canceled. Alternatively, when SLOP that is a value proportional to the contrast is equal to or less than a predetermined value, it is determined that the subject has low contrast and the reliability of the calculated shift amount is low, and the calculated shift amount x is canceled. As shown in FIG. 18C, when the degree of correlation of a pair of data is low and there is no drop in the correlation amount C (k) between the shift ranges kmin to kmax, the minimum value C (x) is obtained. In such a case, it is determined that the focus cannot be detected.

When it is determined that the calculated shift amount x is reliable, the defocus amount DEF of the subject image plane with respect to the planned image formation plane can be obtained by Expression (7).
DEF = KX · PY · x (7)
In equation (7), PY is a detection pitch (the pitch of focus detection pixels), and KX is the size of the opening angle of the center of gravity of a light beam passing through a pair of distance measurement pupils (the distance measurement pupil center distance and distance measurement). Conversion coefficient determined by the pupil distance).

<< Modification of focus detection element >>
FIG. 19 is an enlarged view of a partial region (region C shown in FIG. 2) of the focus detection element 221A of the modified example. In the focus detection pixel array of the focus detection element 221 illustrated in FIG. 4, an example in which an image shift between the direction D1 and the direction D2 of the photographing screen (direction inclined by ± 45 degrees with respect to the vertical direction of the screen) is illustrated. The focus detection element 221A of this modification detects an image shift in the vertical direction (direction D3) and the horizontal direction (direction D4) of the shooting screen. In general, many artifacts and natural objects to be photographed have a vertical and horizontal structure with respect to the ground plane, and focus detection performance is improved by setting the image shift detection direction to the vertical and horizontal directions of the screen. be able to.

  In FIG. 19, the entire pixel array including the focus detection pixels 340 and 350 is a dense square lattice array as with the imaging pixels. The entire pixel array is further composed of a partial array composed of focus detection pixels 340 shown in FIG. 20 and a partial array composed of focus detection pixels 350 shown in FIG. The focus detection pixels 340 constituting the partial array shown in FIG. 20 are obtained by rotating the focus detection pixels including the microlens 10 and the pair of photoelectric conversion units 12 and 13 shown in FIG. 9 by 90 degrees in the clockwise direction. It is. On the other hand, the focus detection pixels 350 constituting the partial array shown in FIG. 21 are the same as the focus detection pixels including the microlens 10 and the pair of photoelectric conversion units 12 and 13 shown in FIG.

  The partial array shown in FIG. 20 includes focus detection pixels 340 in which the inter-pixel distance between the focus detection pixels shown in FIG. 7 is S2. As described above, the inter-pixel distance S2 is the next shortest inter-pixel distance when the shortest inter-pixel distance in the dense square lattice arrangement is S1, as shown in FIG. In this partial arrangement, the row of focus detection pixels 340 arranged on a straight line in the direction D3 (vertical direction) constitutes one focus detection pixel row, and an image in the direction D3 of a pair of images by the pupil division method. The amount of deviation is detected.

  The partial array shown in FIG. 21 includes focus detection pixels 350 whose inter-pixel distance is S2. As described above, the inter-pixel distance S2 is the next shortest inter-pixel distance when the shortest inter-pixel distance in the dense square lattice arrangement is S1. In this partial arrangement, a row of focus detection pixels 350 arranged on a straight line in the direction D4 (horizontal direction) constitutes one focus detection pixel row, and an image in the direction D4 of a pair of images by the pupil division method. The amount of deviation is detected.

  By arranging the partial array shown in FIG. 20 and the partial array shown in FIG. 21 in combination, a pixel array in which the focus detection pixels shown in FIG. 19 are arranged in a dense square lattice is formed. According to the focus detection element 221A having the pixel array shown in FIG. 19, it is possible to detect an image shift in the D3 direction (vertical direction) and the D4 direction (horizontal direction) at an arbitrary position on the shooting screen.

<< Other Modifications of Focus Detection Element >>
FIG. 22 is an enlarged view of a partial region (region C shown in FIG. 2) of the focus detection element 221B of another modification. In the focus detection pixel array of the focus detection element 221 shown in FIG. 4, one focus is used to detect an image shift between the direction D1 and the direction D2 (direction inclined ± 45 degrees with respect to the vertical direction of the screen) of the shooting screen. An example in which a pair of photoelectric conversion units is provided in the detection pixel is shown. In the focus detection element 221B of this modification, one of the pair of photoelectric conversion units is provided in one focus detection pixel, and the other photoelectric conversion unit is provided in the other focus detection pixel. Two focus detection pixels are adjacent in the image shift detection direction, and image shift detection is performed by arranging such focus detection pixel pairs in the image shift detection direction. With such a configuration, it is possible to simplify the pixel structure and prevent the circuit configuration of the focus detection element from becoming complicated.

  In FIG. 22, the entire pixel array composed of focus detection pixels 360a and 360b and focus detection pixels 370a and 370b is a dense square lattice array similar to the imaging pixels. The entire pixel array is further composed of a partial array composed of focus detection pixels 360a and 360b shown in FIG. 23 and a partial array composed of focus detection pixels 370a and 370b shown in FIG.

  The focus detection pixels 360a and 360b constituting the partial array shown in FIG. 23 rotate the focus detection pixels including the microlens 10 and the pair of photoelectric conversion units 12 and 13 shown in FIG. 9 by 45 degrees in the clockwise direction. It is a thing. Only one photoelectric conversion unit 13 is arranged in the focus detection pixel 360a, and only the other photoelectric conversion unit 12 is arranged in the focus detection pixel 360b.

  The focus detection pixels 370a and 370b constituting the partial array shown in FIG. 24 rotate the focus detection pixel including the microlens 10 and the pair of photoelectric conversion units 12 and 13 shown in FIG. 9 by 45 degrees counterclockwise. It is a thing. Only one photoelectric conversion unit 13 is arranged in the focus detection pixel 370a, and only the other photoelectric conversion unit 12 is arranged in the focus detection pixel 370b.

  The partial array shown in FIG. 23 includes focus detection pixels 360a and 360b in which the inter-pixel distance between the focus detection pixels shown in FIG. 7 is S2. As described above, the inter-pixel distance S2 is the next shortest inter-pixel distance when the shortest inter-pixel distance in the dense square lattice arrangement is S1, as shown in FIG. In this partial arrangement, columns of focus detection pixels 360a and 360b arranged on a straight line in the direction D1 (a direction rotated 45 degrees counterclockwise from the vertical direction) form one focus detection pixel column, and the pupil The image shift amount in the direction D1 of the pair of images is detected by the division method.

  The partial array shown in FIG. 24 includes focus detection pixels 370a and 370b whose inter-pixel distance is S2. As described above, the inter-pixel distance S2 is a distance between the next shortest pixels when the shortest inter-pixel distance in the dense square lattice arrangement is S1. In this partial arrangement, a column of focus detection pixels 370a and 370b arranged on a straight line in the direction D2 (a direction rotated 45 degrees clockwise from the vertical direction and a direction orthogonal to the direction D1) is one focus detection. A pixel row is formed, and an image shift amount in the direction D2 of the pair of images is detected by a pupil division method.

  By arranging the partial arrangement shown in FIG. 23 and the partial arrangement shown in FIG. 24 in combination, a pixel arrangement in which the focus detection pixels shown in FIG. 22 are arranged in a dense square lattice is formed. According to the focus detection element 221B having the pixel array shown in FIG. 22, it is possible to detect an image shift in the D1 direction and the D2 direction at an arbitrary position on the photographing screen.

<< Other Modifications of Focus Detection Element >>
FIG. 25 is an enlarged view of a partial region (region C shown in FIG. 2) of the focus detection element 221C of another modification. In the focus detection pixel array of the focus detection element 221A shown in FIG. 19, in order to detect an image shift in the direction D3 (vertical direction) and the direction D4 (horizontal direction), a pair of focus detection pixels The example provided with the photoelectric conversion part was shown. In the focus detection element 221C of this modified example, one of the pair of photoelectric conversion units is provided in one focus detection pixel, and the other photoelectric conversion unit is provided in the other focus detection pixel. Two focus detection pixels are adjacent in the image shift detection direction, and image shift detection is performed by arranging such focus detection pixel pairs in the image shift detection direction. With such a configuration, it is possible to simplify the pixel structure and prevent the circuit configuration of the focus detection element from becoming complicated.

  In FIG. 25, the entire pixel array composed of the focus detection pixels 380a and 380b and the focus detection pixels 390a and 390b is a dense square lattice array similar to the imaging pixels. The entire pixel array is further composed of a partial array composed of focus detection pixels 380a and 380b shown in FIG. 26 and a partial array composed of focus detection pixels 390a and 390b shown in FIG.

  The focus detection pixels 380a and 380b constituting the partial array shown in FIG. 26 rotate the focus detection pixels including the microlens 10 and the pair of photoelectric conversion units 12 and 13 shown in FIG. 9 by 90 degrees in the clockwise direction. However, only one photoelectric conversion unit 13 is arranged in the focus detection pixel 380a, and only the other photoelectric conversion unit 12 is arranged in the focus detection pixel 380b.

  The focus detection pixels 390a and 390b constituting the partial array shown in FIG. 27 are the same as the focus detection pixels including the microlens 10 and the pair of photoelectric conversion units 12 and 13 shown in FIG. Only one photoelectric conversion unit 13 is disposed in the pixel 390a, and only the other photoelectric conversion unit 12 is disposed in the focus detection pixel 390b.

  The partial array illustrated in FIG. 26 includes focus detection pixels 380a and 380b in which the inter-pixel distance between the focus detection pixels illustrated in FIG. 7 is S2. As described above, the inter-pixel distance S2 is the next shortest inter-pixel distance when the shortest inter-pixel distance in the dense square lattice arrangement is S1, as shown in FIG. In this partial arrangement, the row of focus detection pixels 380a and 380b arranged on a straight line in the direction D3 (vertical direction) constitutes one focus detection pixel row, and a pair of image directions D3 is obtained by the pupil division method. Is detected.

  The partial array shown in FIG. 27 includes focus detection pixels 390a and 390b whose inter-pixel distance is S2. As described above, the inter-pixel distance S2 is the next shortest inter-pixel distance when the shortest inter-pixel distance in the dense square lattice arrangement is S1. In this partial arrangement, the row of focus detection pixels 390a and 390b arranged on a straight line in the direction D4 (horizontal direction) constitutes one focus detection pixel row, and a pair of image directions D4 is obtained by the pupil division method. Is detected.

  The partial array shown in FIG. 26 and the partial array shown in FIG. 27 are combined to form a pixel array in which the focus detection pixels shown in FIG. 25 are arranged in a dense square lattice. According to the focus detection element 221C having the pixel array shown in FIG. 25, it is possible to detect image shift in the D3 direction (vertical direction) and the D4 direction (horizontal direction) at an arbitrary position on the shooting screen.

<< Other Modifications of Focus Detection Element >>
FIG. 28 is an enlarged view of a partial region (region C shown in FIG. 2) of the focus detection element 221D of the modification. In the focus detection pixel array of the focus detection element 221 shown in FIG. 4, an example in which the focus detection pixels are arrayed in a dense square lattice array is shown. However, for example, a dense hexagonal lattice array may be used as another dense array. it can. With such a configuration, the image shift detection direction can be increased, and the focus detection performance can be improved.

  The entire pixel array including the focus detection pixels 410, 420, and 430 is a dense hexagonal lattice array. The entire pixel array further includes a partial array including focus detection pixels 410 illustrated in FIG. 29, a partial array including focus detection pixels 420 illustrated in FIG. 30, and a partial array including focus detection pixels 430 illustrated in FIG. It consists of and.

  The focus detection pixels 410 constituting the partial array shown in FIG. 29 are the same as the focus detection pixels including the microlens 10 and the pair of photoelectric conversion units 12 and 13 shown in FIG. Further, the focus detection pixel 420 constituting the partial array shown in FIG. 30 rotates the focus detection pixel including the microlens 10 and the pair of photoelectric conversion units 12 and 13 shown in FIG. 9 by 60 degrees in the clockwise direction. It is a thing. Further, the focus detection pixels 430 constituting the partial array shown in FIG. 31 rotate the focus detection pixels including the microlens 10 and the pair of photoelectric conversion units 12 and 13 shown in FIG. 9 by 60 degrees counterclockwise. It has been made.

  In the partial array shown in FIG. 29, as shown in FIG. 32, it is composed of focus detection pixels 410 in which the inter-pixel distance between the focus detection pixels is S4. In FIG. 32, the inter-pixel distance S4 is the shortest inter-pixel distance after the inter-pixel distance S3, where S3 is the shortest inter-pixel distance in the dense hexagonal lattice arrangement. In the dense hexagonal lattice arrangement, for example, when P is the shortest inter-pixel distance S3, the second shortest inter-pixel distance S4 is {√ (3) / 2} · P. In this partial arrangement, the row of focus detection pixels 410 arranged on a straight line in the direction D4 (horizontal direction) constitutes one focus detection pixel row, and an image of the pair of images in the direction D4 is obtained by the pupil division method. The amount of deviation is detected.

  The partial array shown in FIG. 30 includes focus detection pixels 420 in which the inter-pixel distance between focus detection pixels is S4 as shown in FIG. As described above, the inter-pixel distance S4 is the shortest inter-pixel distance after the inter-pixel distance S3, where S3 is the shortest inter-pixel distance in the dense hexagonal lattice arrangement. In this partial arrangement, a row of focus detection pixels 420 arranged on a straight line in the direction D5 (a direction rotated 30 degrees counterclockwise from the vertical direction) constitutes one focus detection pixel row, and the pupil division method Thus, the image shift amount in the direction D5 of the pair of images is detected.

  The partial array shown in FIG. 31 includes focus detection pixels 430 in which the inter-pixel distance between focus detection pixels is S4 as shown in FIG. The inter-pixel distance S4 is the shortest inter-pixel distance after the inter-pixel distance S3, where S3 is the shortest inter-pixel distance in the dense hexagonal lattice arrangement. In this partial arrangement, a row of focus detection pixels 430 arranged on a straight line in the direction D6 (a direction rotated 30 degrees clockwise from the vertical direction) constitutes one focus detection pixel row, and is divided by a pupil division method. An image shift amount in the direction D6 of the pair of images is detected.

  By arranging the partial array shown in FIG. 29, the partial array shown in FIG. 30, and the partial array shown in FIG. 31 in combination, a pixel array in which the focus detection pixels shown in FIG. 28 are arranged in a dense hexagonal lattice is formed. According to the focus detection element 221D having the pixel array shown in FIG. 28, it is possible to detect an image shift in the D4 direction, the D5 direction, and the D6 direction at an arbitrary position on the shooting screen.

<< Other Modifications of Focus Detection Element >>
FIG. 33 is an enlarged view of a partial region (region C shown in FIG. 2) of the focus detection element 221E of the modification. The focus detection pixel array of the focus detection element 221D shown in FIG. 28 includes a pair of photoelectric conversion units in one focus detection pixel in order to detect image misalignment in the direction D4, the direction D5, and the direction D6. An example was given. In the focus detection element 221E of this modification, one of the pair of photoelectric conversion units is provided in one focus detection pixel, and the other photoelectric conversion unit is provided in the other focus detection pixel. Two focus detection pixels are adjacent in the image shift detection direction, and image shift detection is performed by arranging such focus detection pixel pairs in the image shift detection direction. With such a configuration, it is possible to simplify the pixel structure and prevent the circuit configuration of the focus detection element from becoming complicated.

  In FIG. 33, the entire pixel array composed of focus detection pixels 440a, 440b, 450a, 450b, 460a, and 460b is a dense hexagonal lattice array. The entire pixel array further includes a partial array including focus detection pixels 440a and 440b illustrated in FIG. 34, a partial array including focus detection pixels 450a and 450b illustrated in FIG. 35, and a focus detection pixel 460a illustrated in FIG. It consists of a partial array consisting of 460b.

  The focus detection pixels 440a and 440b constituting the partial array shown in FIG. 34 are the same as the focus detection pixels including the microlens 10 and the pair of photoelectric conversion units 12 and 13 shown in FIG. Only one photoelectric conversion unit 13 is arranged in the pixel 440a, and only the other photoelectric conversion unit 12 is arranged in the focus detection pixel 440b.

  The focus detection pixels 450a and 450b constituting the partial array shown in FIG. 35 are obtained by rotating the focus detection pixel including the microlens 10 and the pair of photoelectric conversion units 12 and 13 shown in FIG. 9 by 60 degrees in the clockwise direction. However, only one photoelectric conversion unit 13 is arranged in the focus detection pixel 450a, and only the other photoelectric conversion unit 12 is arranged in the focus detection pixel 450b.

  The focus detection pixels 460a and 460b constituting the partial array shown in FIG. 36 rotate the focus detection pixels including the microlens 10 and the pair of photoelectric conversion units 12 and 13 shown in FIG. 9 by 60 degrees counterclockwise. However, only one photoelectric conversion unit 13 is arranged in the focus detection pixel 460a, and only the other photoelectric conversion unit 12 is arranged in the focus detection pixel 460b.

  The partial array shown in FIG. 34 includes focus detection pixels 440a and 440b in which the inter-pixel distance between the focus detection pixels shown in FIG. 32 is S4. The inter-pixel distance S4 is the next shortest inter-pixel distance when the shortest inter-pixel distance in the dense hexagonal lattice arrangement is S3 as shown in FIG. In this partial arrangement, the row of focus detection pixels 440a and 440b arranged on a straight line in the direction D4 (horizontal direction) constitutes one focus detection pixel row, and a pair of image directions D4 is obtained by the pupil division method. Is detected.

  The partial array illustrated in FIG. 35 includes focus detection pixels 450a and 450b in which the inter-pixel distance between the focus detection pixels illustrated in FIG. 32 is S4. As described above, the inter-pixel distance S4 is the next shortest inter-pixel distance when the shortest inter-pixel distance in the dense hexagonal lattice arrangement is S3. In this partial arrangement, a row of focus detection pixels 450a and 450b arranged on a straight line in the direction D5 (a direction rotated 30 degrees counterclockwise from the vertical direction) constitutes one focus detection pixel row, and the pupil The image shift amount in the direction D5 of the pair of images is detected by the division method.

  The partial array shown in FIG. 36 includes focus detection pixels 460a and 460b in which the inter-pixel distance between the focus detection pixels shown in FIG. 32 is S4. As described above, the inter-pixel distance S4 is the next shortest inter-pixel distance when the shortest inter-pixel distance in the dense hexagonal lattice arrangement is S3. In this partial arrangement, columns of focus detection pixels 460a and 460b arranged on a straight line in the direction D6 (a direction rotated 30 degrees clockwise from the vertical direction) constitute one focus detection pixel column, and pupil division is performed. The image shift amount in the direction D6 of the pair of images is detected by the method.

  By arranging the partial array shown in FIG. 34, the partial array shown in FIG. 35, and the partial array shown in FIG. 36 in combination, a pixel array in which the focus detection pixels shown in FIG. 33 are arranged in a dense hexagonal lattice is formed. According to the focus detection element 221E having the pixel array shown in FIG. 33, it is possible to detect an image shift in the D4 direction, the D5 direction, and the D6 direction at an arbitrary position on the shooting screen.

  As described above, in one embodiment, focus detection pixels 320, 330,... Having photoelectric conversion units 12, 13 that convert an optical image formed by a light beam coming from the interchangeable lens 202 into an electrical signal. Are densely arranged two-dimensionally, the array of focus detection pixels 320, 330,... Is composed of a plurality of partial arrays, and the shortest adjacent focus detection pixels belonging to each partial array The inter-pixel distance is the shortest inter-pixel distance after the shortest adjacent pixel distance in the dense focus detection pixel array, and the focus detection pixels belonging to the same partial array are the exit pupils of the interchangeable lens 202. 1 have photoelectric conversion units 12 and 13 that receive light beams passing through a pair of regions arranged in one of the alignment directions of the focus detection pixels in the partial arrays. Out pixels 320 and 330, the photoelectric conversion portions 12 and 13 of ... are constituted as the direction of arrangement of the pair of regions of the exit pupil of the interchangeable lens 202 through which light beams received are different. Thereby, it is possible to realize focus detection with high accuracy in a plurality of directions with an equivalent performance at an arbitrary position on the photographing screen of the interchangeable lens 202.

<< Other modifications >>
In the embodiment described above, the focus detection pixel interval (inter-pixel distance) in each partial array is set to the second shortest interval among the densely arranged focus detection pixel intervals. Although an example in which a plurality of focus detection pixels are arranged along the line is shown, the focus detection pixels may be arranged along the direction of the third or fourth shortest interval.

  In the above-described embodiment, the example in which the focus detection pixel array plane of the focus detection element covers an area smaller than the shooting screen is shown. However, the magnitude relationship between the shooting screen and the focus detection pixel array plane is shown here. The present invention is not limited, and the two may be made equal to each other according to the situation, or the focus detection pixel array surface may be made larger than the shooting screen.

  In the above-described embodiment, the example in which the light receiving surface size of the focus detection pixel is larger than the light receiving surface size of the imaging pixel is shown. However, the light receiving surface size of the focus detection pixel and the light receiving surface size of the imaging pixel are The magnitude relationship is not limited to this, and both may be made equal according to the situation, or the light receiving surface size of the focus detection pixel may be made smaller than the light receiving surface size of the imaging pixel.

  In the above-described embodiment, an example in which the imaging optical path is divided into two using a half mirror, an imaging element is arranged in the transmission optical path, and a focus detection element is arranged in the reflection optical path has been described. The arrangement of elements may be reversed.

  In the above-described embodiment, the imaging optical path is divided into two by using a fixed half mirror, and an imaging element and a focus detection element are arranged in each of the divided optical paths so that the focus detection operation and the imaging operation are performed simultaneously. The optical path is switched by putting the quick return mirror into and out of the optical path, and an image sensor and a focus detection element are arranged in each switched optical path so that the focus detection operation and the imaging operation are performed in a time-sharing manner. It may be configured.

  In the above-described embodiment, the data of the focus detection element is not used as image data. However, the dynamic range may be expanded by combining the data with the image data of the imaging element as a luminance signal.

  In the embodiment described above, the data of the focus detection element is used only for focus detection, but it can also be used as photometric data for exposure control of the image sensor. Thereby, the photometric sensor can be omitted.

  In the embodiment described above, the data of the focus detection element is used only for focus detection, but it can also be used as blur detection data for image blur detection of the image sensor. Thereby, an image sensor dedicated to image blur detection can be omitted.

  In the embodiment described above, the data of the focus detection element is used for image shift detection, but it can also be used for contrast detection.

  In the embodiment described above, the spectral sensitivity of the focus detection pixel of the focus detection element is close to white as shown in FIG. 11, but the sensitivity of the focus detection pixel is within the spectral sensitivity shown in FIG. One may be used. Further, focus detection pixels having different spectral sensitivities may coexist in one focus detection element.

  In the above-described embodiment, the distance detection pupil (distance d0 shown in FIG. 14) set by the focus detection pixels has a single distance. However, for focus detection having different distance detection pupil distances. Pixels may coexist in one focus detection element.

  In the embodiment described above, the image data of the imaging pixels is not used for focus detection, but is used for focus detection of the contrast detection method, and the focus detection result by the focus detection element and the focus detection result by the contrast method are used. You may make it use together.

  In the above-described embodiment, the light beam is divided by the half mirror 222 so as not to depend on the wavelength, but the light beam can also be divided by the spectroscopic mirror. For example, a mirror that divides into an infrared light component and a visible light component is received, the visible light component is received by the image sensor, the infrared light component is received by the focus detection element, and the focus detection result of the focus detection element is converted into the infrared light. By correcting according to the amount of aberration, the focus detection result of visible light can be corrected and used. In this way, it is possible to prevent the amount of visible light received by the image sensor from being reduced by the half mirror.

  In the above-described embodiment, the light beam is split by the light splitting prism 223. However, a half mirror using a thin glass plate or a pellicle half mirror may be used.

  In the embodiment described above, the half mirror 222 may be formed of a multilayer film, or as a polarizing mirror (for example, a polarization component parallel to the paper surface of FIG. 1 is reflected and a polarization component perpendicular to the paper surface is transmitted). It may be formed.

  In the embodiment described above, the lens built in the interchangeable lens side is moved in the optical axis direction for focus adjustment. However, the light splitting prism 223, the focus detection element, and the image sensor in the camera body are unitized. The unit may be moved in the optical axis direction, or the focal point may be roughly adjusted by moving the lens in the optical axis direction, and the focal point may be finely adjusted by moving the unit.

  The present invention is not limited to a focus detection element having focus detection pixels of a pupil division type phase difference detection method using a microlens, and focus detection having focus detection pixels of another type of pupil division type phase difference detection method. It can also be applied to elements. For example, the present invention can be applied to a focus detection element including focus detection pixels of a pupil division type phase difference detection method using polarized light.

  The focus detection element in the above-described embodiment may be a CCD image sensor or a CMOS image sensor.

  The imaging apparatus according to the present invention is not limited to a digital still camera in which an interchangeable lens is mounted on a camera body, and can also be applied to a lens-integrated digital still camera or video camera. Furthermore, the present invention can be applied to a small camera module or a surveillance camera built in a mobile phone or the like. Alternatively, the present invention can be applied to a focus detection device other than a camera, a distance measuring device, or a stereo distance measuring device.

1 is a cross-sectional view illustrating a configuration of an imaging apparatus (camera) according to an embodiment. The figure which shows the arrangement | sequence range of the pixel for imaging and the pixel for focus detection in the imaging | photography screen of an interchangeable lens Partial enlargement of the image sensor The figure which expanded the one part area | region (area | region C shown in FIG. 2) of a focus detection element. The figure which shows one partial arrangement | sequence of the pixel for a focus detection which comprises the focus detection element shown in FIG. The figure which shows the other partial arrangement | sequence of the pixel for focus detection which comprises the focus detection element shown in FIG. The figure which shows the distance between the pixels in the arrangement in the dense square lattice form The figure which expanded the unit arrangement part in the pixel arrangement for image pick-ups of an image sensor Enlarged view of focus detection pixels Diagram showing spectral characteristics of imaging pixels The figure which shows the spectral characteristic of the pixel for focus detection Cross-sectional view of imaging pixels Cross section of focus detection pixel The figure explaining the focus detection method by the pupil division method using a micro lens The figure explaining the relationship between the imaging pixel of an image sensor, and an exit pupil Front view of ranging pupil on exit pupil plane Flowchart showing the operation of the camera (imaging device) shown in FIG. The figure explaining the detail of image shift detection calculation processing (correlation calculation processing) The figure which expanded some fields of the focus detection element of a modification The figure which shows the partial arrangement | sequence of the pixel for a focus detection of the focus detection element shown in FIG. The figure which shows the other partial arrangement | sequence of the pixel for a focus detection of the focus detection element shown in FIG. The figure which expanded the one part area | region of the focus detection element of another modification. The figure which shows the partial arrangement | sequence of the pixel for a focus detection of the focus detection element shown in FIG. The figure which shows the other partial arrangement | sequence of the pixel for a focus detection of the focus detection element shown in FIG. The figure which expanded the one part area | region of the focus detection element of another modification. The figure which shows the partial arrangement | sequence of the pixel for a focus detection of the focus detection element shown in FIG. The figure which shows the other partial arrangement | sequence of the pixel for a focus detection of the focus detection element shown in FIG. The figure which expanded the one part area | region of the focus detection element of another modification. The figure which shows the partial arrangement | sequence of the pixel for a focus detection of the focus detection element shown in FIG. The figure which shows the other partial arrangement | sequence of the pixel for focus detection of the focus detection element shown in FIG. The figure which shows the other partial arrangement | sequence of the pixel for focus detection of the focus detection element shown in FIG. Diagram showing the distance between pixels in a dense hexagonal lattice arrangement The figure which expanded the one part area | region of the focus detection element of another modification. The figure which shows the partial arrangement | sequence of the pixel for a focus detection of the focus detection element shown in FIG. The figure which shows the other partial arrangement | sequence of the pixel for a focus detection of the focus detection element shown in FIG. The figure which shows the other partial arrangement | sequence of the pixel for a focus detection of the focus detection element shown in FIG.

Explanation of symbols

12, 13 Photoelectric conversion unit 202 Interchangeable lens 203 Camera body 206 Lens drive control circuit 214 Body drive control circuit 220 Image sensor 221, 221A-221E Focus detection element 223 Light splitting prisms 320, 330, 340, 350, 360a, 260b, 270a 270b, 380a, 380b, 410, 420, 430, 440a, 440b, 450a, 450b, 460a, 460b Focus detection pixels

Claims (10)

A focus detection element in which a plurality of focus detection pixels that receive light from the imaging optical system are closely arranged in a square lattice;
  Focus detection means for performing focus detection of the imaging optical system based on an output signal from the focus detection element,
  The plurality of focus detection pixels include a plurality of first focus detection pixels arranged in a first direction that forms an angle of 45 degrees with one dense direction of the square lattice, and a first orthogonal to the first direction. A plurality of second focus detection pixels arranged in two directions,
  The first focus detection pixels are arranged every other pixel in two dense directions orthogonal to the square lattice, and the second focus detection pixels are positions where the first focus detection pixels are not arranged. Are arranged every other pixel in two dense directions perpendicular to the square lattice,
  The first focus detection pixel has a pair of photoelectric conversion units divided in a direction perpendicular to the first direction,
  The second focus detection pixel has a pair of photoelectric conversion units divided in a direction perpendicular to the second direction,
  The focus detection means performs focus detection based on the output signals of the pair of photoelectric conversion units of the first focus detection pixel, and focuses based on the output signals of the pair of photoelectric conversion units of the second focus detection pixel. A focus detection apparatus characterized by detecting. The focus detection apparatus according to claim 1,
  The first focus detection pixel includes a microlens, and the pair of photoelectric conversion units of the first focus detection pixel transmits light beams that have passed through different regions of the exit pupil of the imaging optical system to the microlens. Through each
  The second focus detection pixel has a microlens, and the pair of photoelectric conversion units of the second focus detection pixel transmits a light beam that has passed through different regions of the exit pupil of the imaging optical system to the microlens. Through each
  The focus detection apparatus, wherein the first and second focus detection pixels have the same spectral sensitivity. A focus detection element in which a plurality of focus detection pixels that receive light from the imaging optical system are closely arranged in a square lattice;
  Focus detection means for performing focus detection of the imaging optical system based on an output signal from the focus detection element,
  The plurality of focus detection pixels include a plurality of first focus detection pixels arranged in a first direction that forms an angle of 45 degrees with one dense direction of the square lattice, and a first orthogonal to the first direction. A plurality of second focus detection pixels arranged in two directions,
  The first focus detection pixels are arranged every other pixel in two dense directions orthogonal to the square lattice, and the second focus detection pixels are positions where the first focus detection pixels are not arranged. Are arranged every other pixel in two dense directions perpendicular to the square lattice,
  When the pixel region is divided in a direction perpendicular to the first direction, the first focus detection pixel has a first pixel having a photoelectric conversion unit in one region and a photoelectric region in the other region. A second pixel having a conversion unit, the first and second pixels are alternately arranged,
  When the pixel region is divided in a direction perpendicular to the second direction, the second focus detection pixel has a first pixel having a photoelectric conversion unit in one region and a photoelectric region in the other region. A second pixel having a conversion unit, the first and second pixels are alternately arranged,
  The focus detection means performs focus detection based on an output signal of the photoelectric conversion unit of the first and second pixels of the first focus detection pixel, and the first and second pixels of the second focus detection pixel. A focus detection apparatus that detects a focus based on an output signal of a photoelectric conversion unit. The focus detection apparatus according to claim 3,
  Each of the first and second pixels of the first focus detection pixel has a microlens;
  The photoelectric conversion units of the first and second pixels of the first focus detection pixel respectively receive light beams that have passed through different areas of the exit pupil of the imaging optical system via the microlens,
  Each of the first and second pixels of the second focus detection pixel has a microlens,
  The photoelectric conversion units of the first and second pixels of the second focus detection pixel respectively receive light beams that have passed through different regions of the exit pupil of the imaging optical system via the microlens,
  The focus detection apparatus according to claim 1, wherein the first and second pixels of the first focus detection pixel and the first and second pixels of the second focus detection pixel have the same spectral sensitivity. A focus detection element in which a plurality of focus detection pixels that receive light from the imaging optical system are densely arranged in a grid of a dense hexagonal lattice;
  Focus detection means for performing focus detection of the imaging optical system based on an output signal from the focus detection element,
  The plurality of focus detection pixels include a plurality of first focus detection pixels arranged in a first direction that forms an angle of 30 degrees with one dense direction of the dense hexagonal lattice, and the first direction and 60 degrees. A plurality of second focus detection pixels arrayed in a second direction having an angle of, and a plurality of third focus arrays arrayed in a third direction having an angle of 60 degrees with the first direction and the second direction. A focus detection pixel;
  The first focus detection pixels are arranged every two pixels in three dense directions of the dense hexagonal lattice, and the second focus detection pixels are arranged at positions where the first focus detection pixels are not arranged. The third focus detection pixels are arranged every two pixels in the three dense directions of the hexagonal lattice, and the dense hexagonal lattice is arranged at a position where the first focus detection pixel and the second focus detection pixel are not disposed. Are arranged every two pixels in the three dense directions of
  The first focus detection pixel has a pair of photoelectric conversion units divided in a direction perpendicular to the first direction,
  The second focus detection pixel has a pair of photoelectric conversion units divided in a direction perpendicular to the second direction,
  The third focus detection pixel has a pair of photoelectric conversion units divided in a direction perpendicular to the third direction,
  The focus detection unit performs focus detection based on output signals of the pair of photoelectric conversion units of the first focus detection pixel, and detects focus based on output signals of the pair of photoelectric conversion units of the second focus detection pixel. A focus detection apparatus that detects a focus based on output signals of the pair of photoelectric conversion units of the third focus detection pixel. The focus detection apparatus according to claim 5,
  The first focus detection pixel includes a microlens, and the pair of photoelectric conversion units of the first focus detection pixel transmits light beams that have passed through different regions of the exit pupil of the imaging optical system to the microlens. Through each
  The second focus detection pixel has a microlens, and the pair of photoelectric conversion units of the second focus detection pixel transmits a light beam that has passed through different regions of the exit pupil of the imaging optical system to the microlens. Through each
  The third focus detection pixel has a microlens, and the pair of photoelectric conversion units of the third focus detection pixel transmits a light beam that has passed through different regions of the exit pupil of the imaging optical system to the microlens. Through each
  The focus detection apparatus, wherein the first, second, and third focus detection pixels have the same spectral sensitivity. A focus detection element in which a plurality of focus detection pixels that receive light from the imaging optical system are densely arranged in a grid of a dense hexagonal lattice;
  Focus detection means for performing focus detection of the imaging optical system based on an output signal from the focus detection element,
  The plurality of focus detection pixels include a plurality of first focus detection pixels arranged in a first direction that forms an angle of 30 degrees with one dense direction of the dense hexagonal lattice, and the first direction and 60 degrees. A plurality of second focus detection pixels arrayed in a second direction having an angle of, and a plurality of third focus arrays arrayed in a third direction having an angle of 60 degrees with the first direction and the second direction. A focus detection pixel;
  The first focus detection pixels are arranged every two pixels in three dense directions of the dense hexagonal lattice, and the second focus detection pixels are arranged at positions where the first focus detection pixels are not arranged. The third focus detection pixels are arranged every two pixels in the three dense directions of the hexagonal lattice, and the dense hexagonal lattice is arranged at a position where the first focus detection pixel and the second focus detection pixel are not disposed. Are arranged every two pixels in the three dense directions of
  When the pixel region is divided in a direction perpendicular to the first direction, the first focus detection pixel has a first pixel having a photoelectric conversion unit in one region and a photoelectric region in the other region. A second pixel having a conversion unit, the first and second pixels are alternately arranged,
  When the pixel region is divided in a direction perpendicular to the second direction, the second focus detection pixel has a first pixel having a photoelectric conversion unit in one region and a photoelectric region in the other region. A second pixel having a conversion unit, the first and second pixels are alternately arranged,
  When the third focus detection pixel divides the pixel region in a direction perpendicular to the third direction, the third focus detection pixel has a first pixel having a photoelectric conversion unit in one region and a photoelectric region in the other region. A second pixel having a conversion unit, the first and second pixels are alternately arranged,
  The focus detection unit performs focus detection based on an output signal of a photoelectric conversion unit of the first and second pixels of the first focus detection pixel, and detects the first and second pixels of the second focus detection pixel. A focus detection apparatus, wherein focus detection is performed based on an output signal of a photoelectric conversion unit, and focus detection is performed based on output signals of photoelectric conversion units of the first and second pixels of the third focus detection pixel. The focus detection apparatus according to claim 7,
  Each of the first and second pixels of the first focus detection pixel has a microlens;
  The photoelectric conversion units of the first and second pixels of the first focus detection pixel respectively receive light beams that have passed through different areas of the exit pupil of the imaging optical system via the microlens,
  Each of the first and second pixels of the second focus detection pixel has a microlens,
  The photoelectric conversion units of the first and second pixels of the second focus detection pixel respectively receive light beams that have passed through different regions of the exit pupil of the imaging optical system via the microlens,
  Each of the first and second pixels of the third focus detection pixel has a microlens,
  The photoelectric conversion units of the first and second pixels of the third focus detection pixel respectively receive light beams that have passed through different regions of the exit pupil of the imaging optical system via the microlens,
  The first and second pixels of the first focus detection pixel, the first and second pixels of the second focus detection pixel, and the first and second pixels of the first focus detection pixel are: A focus detection apparatus having the same spectral sensitivity. The focus detection apparatus according to any one of claims 1 to 8,
Focus adjusting means for adjusting the focus of the imaging optical system based on the focus detection result of the focus detecting means;
An imaging apparatus comprising: an imaging device in which a plurality of imaging pixels that receive light from the imaging optical system are densely arranged two-dimensionally . The imaging device according to claim 9,
An image pickup apparatus comprising: an optical unit that guides a light beam that has passed through the imaging optical system to the focus detection element and the image pickup element .

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